I got a lead on 3 Ford Dealers that show these storage units in stock. I just bought a MM trunk organizer unit w/carpeted top from one of them. Fits perfect in my MM. They were sold for Crown Vics and Grand Marquis.
Its Part #: 2W7Z54115A00AA
OEM: Ford
Desc: COMPARTMENT ASY - REAR STOWAGE
Try: Bobby Jones Ford, Augusta, Ga 706 738-8000
or
Parts Midwest Inc has two.
Minneapolis, MN 612 331-4860